In wells including submersible pumps for pumping water up through long flexible plastic tubing (hereafter "well pipe"), pipe, removal of the well pipe is difficult as this procedure is labour intensive and time consuming. Traditional well management systems can be employed to achieve this result, e.g. a tower crane. This, however, is a costly proposition.
Various other attempts to manage the hoisting of well pipe have been made in the art such as that disclosed in U.S. Pat. No. 4,655,291. In this document, Cox discloses an apparatus for running pipe into or out of a well. The apparatus includes a dual roller system with a complicated network of springs, gears, chains, etc. The apparatus of this invention, since it includes numerous moving parts is susceptible to wear etc., which limits its usefulness.
In Canadian Patent No. 695,744, there is disclosed an apparatus for delivering pipe to a well which includes a spool carrying relatively inflexible well pipe to be fed into or removed from a well. This is done using a first feed-wheel which cooperates with a series of smaller straightening wheels which act as straightening rollers to deliver the pipe into the well in a linear condition. This same apparatus is said to also permit retrieval of well pipe.
Other patent documents related to the field of this invention include the following U.S. Pat. Nos. 3,168,287; 2,670,926; 3,809,366; 3,871,618; 4,296,916 and 3,791,625.
In Parola (U.S. Pat. No. 3,168,287) flexible well pipe is wound around a pulling drum several turns in order to lift the pipe from the well. The well pipe is grasped by the radial constrictive force caused by the encirclement of the cylindrical core of the drum by the pipe.
In Sewell (U.S. Pat. No. 2,670,926) flexible cable is drawn-in by a pair of opposed pneumatic tires that pinch the cable between the flat cylindrical faces of the two tires. The cable is fed straight through the "pinch" created by the two tires.
In Funk (U.S. Pat. No. 3,871,618) three obliquely opposed tires are used to pull well pipe in the manner of Sewell.
In Crees (U.S. Pat. No. 3,809,366) flexible electrical cable is fed by frictional engagement over a grooved spool or pulley into conduit. This pulley is shown in one embodiment (FIG. 2) as having an "arcuate" end or groove (44) for engagement of the conduit. Additional frictional engagement with the conduit is said to be effected in another embodiment (FIG. 3) by helically wrapping the conduit around the pulley for several turns. The embodiment of FIG. 1 shows a half-turn engagement between the conduit and pulley, enforced by the presence of a protective casing cover (21).
In Jewett (U.S. Pat. No. 4,296,916) a cable-carrying winch is shown mounted at a well-head for lifting a submersible well pump from the well bottom by cable.
Viljoen (U.S. Pat. No. 3,791,625) is a patent directed to hauling fish nets from the water. A powered V-shaped sheave in conjunction with a constant-pressure wheel is used to shape the net to resist shearing of the netting strands. The sheave surface is shown as being purely conical or "V"-shaped in cross-section in the region where it engages with the net.
The present invention addresses the problem of providing a hoisting mechanism for pulling from a well a length of flexible well pipe utilizing a hoisting system that allows the operator to readily engage, and disengage, the pipe as required during the well pipe removal operation. This is effected by a pipe-engaging mechanism that differs from the prior art both as to its structure and in the convenience of its use.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.